In the past, a technique has been proposed in which “the joined surface between a housing and a fixed scroll is divided into a sealed surface and a welded surface by being formed in a stepped formation, and laser welding is performed across the entire external periphery of the welded surface to join the housing and the fixed scroll together” (see Japanese Laid-open Patent Application No. 2002-195171, for example). A technique for laser welding has also been proposed in the past, in which “a pure nickel thin film is sandwiched between cast iron and steel, and the steel side is irradiated with laser light to weld the cast iron and steel” (see Japanese Laid-open Patent Application No. 2001-334378, for example).